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Improved JccMov1JmpMov0Jmp -> SETcc optimisation

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This commit is contained in:
J. Gareth "Curious Kit" Moreton 2022-01-30 14:27:17 +00:00 committed by FPK
parent 89e0282856
commit c4ea01cf3d
1 changed files with 222 additions and 3 deletions
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225
compiler/x86/aoptx86.pas
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@ -138,6 +138,7 @@ unit aoptx86;
function DoSubAddOpt(var p : tai) : Boolean;
function DoMovCmpMemOpt(var p : tai; const hp1: tai; UpdateTmpUsedRegs: Boolean) : Boolean;
function DoSETccLblRETOpt(var p: tai; const hp_label: tai_label) : Boolean;
function PrePeepholeOptSxx(var p : tai) : boolean;
function PrePeepholeOptIMUL(var p : tai) : boolean;
@ -5406,6 +5407,214 @@ unit aoptx86;
end;
function TX86AsmOptimizer.DoSETccLblRETOpt(var p: tai; const hp_label: tai_label) : Boolean;
var
hp2, hp3, hp4, hp5, hp6: tai;
ThisReg: TRegister;
JumpLoc: TAsmLabel;
begin
Result := False;
{
Convert:
j<c> .L1
.L2:
mov 1,reg
jmp .L3 (or ret, although it might not be a RET yet)
.L1:
mov 0,reg
jmp .L3 (or ret)
( As long as .L3 <> .L1 or .L2)
To:
mov 0,reg
set<not(c)> reg
jmp .L3 (or ret)
.L2:
mov 1,reg
jmp .L3 (or ret)
.L1:
mov 0,reg
jmp .L3 (or ret)
}
if JumpTargetOp(taicpu(p))^.ref^.refaddr<>addr_full then
Exit;
JumpLoc := TAsmLabel(JumpTargetOp(taicpu(p))^.ref^.symbol);
if GetNextInstruction(hp_label, hp2) and
MatchInstruction(hp2,A_MOV,[]) and
(taicpu(hp2).oper[0]^.typ = top_const) and
(
(
(taicpu(hp2).oper[1]^.typ = top_reg)
{$ifdef i386}
{ Under i386, ESI, EDI, EBP and ESP
don't have an 8-bit representation }
and not (getsupreg(taicpu(hp2).oper[1]^.reg) in [RS_ESI, RS_EDI, RS_EBP, RS_ESP])
{$endif i386}
) or (
{$ifdef i386}
(taicpu(hp2).oper[1]^.typ <> top_reg) and
{$endif i386}
(taicpu(hp2).opsize = S_B)
)
) and
GetNextInstruction(hp2, hp3) and
MatchInstruction(hp3, A_JMP, A_RET, []) and
(
(taicpu(hp3).opcode=A_RET) or
(
(taicpu(hp3).oper[0]^.ref^.refaddr=addr_full) and
(tasmlabel(taicpu(hp3).oper[0]^.ref^.symbol)<>tai_label(hp_label).labsym)
)
) and
GetNextInstruction(hp3, hp4) and
SkipAligns(hp4, hp4) and
(hp4.typ=ait_label) and
(tai_label(hp4).labsym=JumpLoc) and
(
not (cs_opt_size in current_settings.optimizerswitches) or
{ If the initial jump is the label's only reference, then it will
become a dead label if the other conditions are met and hence
remove at least 2 instructions, including a jump }
(JumpLoc.getrefs = 1)
) and
{ Don't check if hp3 jumps to hp4 because this is a zero-distance jump
that will be optimised out }
GetNextInstruction(hp4, hp5) and
MatchInstruction(hp5,A_MOV,[taicpu(hp2).opsize]) and
(taicpu(hp5).oper[0]^.typ = top_const) and
(
((taicpu(hp2).oper[0]^.val = 0) and (taicpu(hp5).oper[0]^.val = 1)) or
((taicpu(hp2).oper[0]^.val = 1) and (taicpu(hp5).oper[0]^.val = 0))
) and
MatchOperand(taicpu(hp2).oper[1]^,taicpu(hp5).oper[1]^) and
GetNextInstruction(hp5,hp6) and
(
(hp6.typ<>ait_label) or
SkipLabels(hp6, hp6)
) and
(hp6.typ=ait_instruction) then
begin
{ First, let's look at the two jumps that are hp3 and hp6 }
if not
(
(taicpu(hp6).opcode=taicpu(hp3).opcode) and { Both RET or both JMP to the same label }
(
(taicpu(hp6).opcode=A_RET) or
MatchOperand(taicpu(hp6).oper[0]^, taicpu(hp3).oper[0]^)
)
) then
{ If condition is False, then the JMP/RET instructions matched conventionally }
begin
{ See if one of the jumps can be instantly converted into a RET }
if (taicpu(hp3).opcode=A_JMP) then
begin
{ Reuse hp5 }
hp5 := getlabelwithsym(TAsmLabel(JumpTargetOp(taicpu(hp3))^.ref^.symbol));
{ Make sure hp5 doesn't jump back to .L2 (infinite loop) }
if not Assigned(hp5) or (hp5=hp4) or not GetNextInstruction(hp5, hp5) then
Exit;
if MatchInstruction(hp5, A_RET, []) then
begin
DebugMsg(SPeepholeOptimization + 'Converted JMP to RET as part of SETcc optimisation (1st jump)', hp3);
ConvertJumpToRET(hp3, hp5);
Result := True;
end
else
Exit;
end;
if (taicpu(hp6).opcode=A_JMP) then
begin
{ Reuse hp5 }
hp5 := getlabelwithsym(TAsmLabel(JumpTargetOp(taicpu(hp6))^.ref^.symbol));
if not Assigned(hp5) or not GetNextInstruction(hp5, hp5) then
Exit;
if MatchInstruction(hp5, A_RET, []) then
begin
DebugMsg(SPeepholeOptimization + 'Converted JMP to RET as part of SETcc optimisation (2nd jump)', hp6);
ConvertJumpToRET(hp6, hp5);
Result := True;
end
else
Exit;
end;
if not
(
(taicpu(hp6).opcode=taicpu(hp3).opcode) and { Both RET or both JMP to the same label }
(
(taicpu(hp6).opcode=A_RET) or
MatchOperand(taicpu(hp6).oper[0]^, taicpu(hp3).oper[0]^)
)
) then
{ Still doesn't match }
Exit;
end;
if (taicpu(hp2).oper[0]^.val = 1) then
begin
taicpu(p).condition := inverse_cond(taicpu(p).condition);
DebugMsg(SPeepholeOptimization + 'J(c)Mov1Jmp/RetMov0Jmp/Ret -> Set(~c)Jmp/Ret',p)
end
else
DebugMsg(SPeepholeOptimization + 'J(c)Mov0Jmp/RetMov1Jmp/Ret -> Set(c)Jmp/Ret',p);
if taicpu(hp2).opsize=S_B then
begin
if taicpu(hp2).oper[1]^.typ = top_reg then
hp4:=taicpu.op_reg(A_SETcc, S_B, taicpu(hp2).oper[1]^.reg)
else
hp4:=taicpu.op_ref(A_SETcc, S_B, taicpu(hp2).oper[1]^.ref^);
hp2 := p;
end
else
begin
{ Will be a register because the size can't be S_B otherwise }
ThisReg:=newreg(R_INTREGISTER,getsupreg(taicpu(hp2).oper[1]^.reg), R_SUBL);
hp4:=taicpu.op_reg(A_SETcc, S_B, ThisReg);
hp2:=taicpu.op_const_reg(A_MOV, taicpu(hp2).opsize, 0, taicpu(hp2).oper[1]^.reg);
{ Inserting it right before p will guarantee that the flags are also tracked }
Asml.InsertBefore(hp2, p);
end;
taicpu(hp4).condition:=taicpu(p).condition;
asml.InsertBefore(hp4, hp2);
JumpLoc.decrefs;
if taicpu(hp3).opcode = A_JMP then
begin
MakeUnconditional(taicpu(p));
taicpu(p).loadref(0, JumpTargetOp(taicpu(hp3))^.ref^);
TAsmLabel(JumpTargetOp(taicpu(hp3))^.ref^.symbol).increfs;
end
else
begin
taicpu(p).condition := C_None;
taicpu(p).opcode := A_RET;
taicpu(p).clearop(0);
taicpu(p).ops := 0;
end;
if (JumpLoc.getrefs = 0) then
RemoveDeadCodeAfterJump(hp3);
Result:=true;
exit;
end;
end;
function TX86AsmOptimizer.OptPass1Sub(var p : tai) : boolean;
var
hp1, hp2: tai;
@ -6805,11 +7014,11 @@ unit aoptx86;
function TX86AsmOptimizer.OptPass1Jcc(var p : tai) : boolean;
var
hp1, hp2, hp3, hp4, hp5: tai;
hp1, hp2, hp3, hp4, hp5, hp6: tai;
ThisReg: TRegister;
begin
Result := False;
if not GetNextInstruction(p,hp1) or (hp1.typ <> ait_instruction) then
if not GetNextInstruction(p,hp1) then
Exit;
{
@ -6966,6 +7175,8 @@ unit aoptx86;
Result:=true;
exit;
end
else if (hp1.typ = ait_label) then
Result := DoSETccLblRETOpt(p, tai_label(hp1));
end;
@ -9847,8 +10058,16 @@ unit aoptx86;
increg, tmpreg: TRegister;
begin
result:=false;
if GetNextInstruction(p,hp1) and (hp1.typ=ait_instruction) then
if GetNextInstruction(p,hp1) then
begin
if (hp1.typ=ait_label) then
begin
Result := DoSETccLblRETOpt(p, tai_label(hp1));
Exit;
end
else if (hp1.typ<>ait_instruction) then
Exit;
symbol := TAsmLabel(taicpu(p).oper[0]^.ref^.symbol);
if (
(